Bet Ol’ Blue Eyes never thought twice about making a dinner reservation, but Frank P. Sinatra Jr., of Freehold, NJ, has learned to be careful.

He was just 21 when he took his then-girlfriend for dinner at the Rainbow Room, shortly after the Chairman of the Board’s death in 1998.

Frank P. – no relation to the legendary crooner – couldn’t believe how quickly they were seated or how well they were treated. Especially when the check came.

“They said, ‘We can’t take your money. You’re grandfather was like a God here,’ ” the now 31-year-old father recalled.

“I looked at my girlfriend and said, ‘We’ve got to get out of here right now.’ ”

The crooner would have turned 93 Friday and, in his honor, those who share his famous name reflected on living life as a Frank Sinatra.

There are at least 14 Frank Sinatras in the New York area, including four listed in New York City.

Five in one family – three generations of Francesco Sinatra men, as well as a cousin Francis and his daughter Francesca – were tapped with the famous moniker simply to carry on family tradition.

They never know which way a conversation is going to go when they give their name.

Francesco Sinatra Sr., 59, of Staten Island, could hardly get rid of TV and Broadway star Tony Danza, who insisted on meeting him in 2005 at the late singer’s West 56th Street haunt, Patsy’s.

Francesco cousin Francis A. Sinatra, 55, of Glendale, Queens, almost didn’t get into Iona College because of his name.

“My mother had sent a check, and I never heard back from them,” he said. “My mother called, and whoever she spoke to said they had just disregarded the application because they thought it was a joke. But they had cashed the check!”

On the other hand, another time a set of golf clubs he ordered unexpectedly arrived via express mail – the company put a rush on the order, thinking he was the Frank Sinatra.

When Francis A. was on businesses at the New York County Clerk’s Office, the clerk insisted on meeting him personally.

“He said, ‘I want to introduce you to someone – this is Calvin Klein,’ ” Sinatra recalled the clerk saying as he was introduced to the designer, who happened to be there for jury duty.